Recording galvanometer



May 3, 1938. J. A. WIDMER ,1

RECORDING GALVANOI IETER 7 Original Filed Feb. 17, 1933 3 Sheets-Sheet 14C. sour? L IN V EN TOR. JvLEa A WIDMER ATTORNEY V Q y 3, 1938. J. A.WIDMER 2,115,831

nscoxbme GALVANOMETER Original Filed Feb. 17, 19s: 3 Shets-Sheet 2INVENTOR. Jazz! A. WIDMEB I AT ORNEY y 3, 1938. 4 J. A. WIDMER 2,115,831

nsconnme GALVANOMETER Original Filed Feb. 17, 1935 s She'et-Sheet 5 INVEN TOR. Juzzs H. MDMER A ORNEY Patented May a, 1m

o es

' ascoanmo osnvsuorm'ran Jules A. Wldmer, Roohester,'N. Y., assignor' toTaylor Instrument Companies, Rochester, N. Y.,

a corporation oi New York Original a cation February 17, 1933, SerialNo.

857,233. vided and this application November 26, 1935, Serial No. 51,618

a cums.

This invention relates to control "systems and more particularly tomechanism for use in motor control systems.

" .In various control systems it is necessary to move a member to apredetermined position and to stop this member in that position withoutany overthrow or oscillating movement about said position. The presentinvention, therefore, has for its main object the provision of a noveland reliable arrangement which accomplishes this result and which is,nevertheless, simple and economical to manufacture.

In its more specific aspects, the invention includes a galvanometerwhich mechanically controls the adjustment of switching mechanismwhereby a reversible motor is selectively operated to adjust a member toa predetermined point without overthrow and without oscillation aboutthis point.

Referring to the drawings, Fig. l diagrammatically represents asimplified showing of the electrical circuits of an automatic recordingpyrometer system; Fig. 2 is a diagrammatic showing of the electricalcircuits and certain portions of the mechanical equipment employed inthe eter system; and Figs. 3 and 4 are respectively a front elevationand a bottom plan view of the mechanism-for operating a switching devieeunder the control of a galvanometer needle.

Referring especially to Fig. 1, there is indicated a conventionalpotentiometer network generally designated I, which includes the battery3, the slide wire resistor I, a stationary wiping contaetor I engagingthis resistor, the thermocouple I, the galvsnometer 'II and theresistors II and I2. An operating network, controlled in part by thepotentiometer network includes a reversible A. C.

the purpose forth.

series 'motor l3 having the field circuits it and I! and the armatureII. The circuits of this motor are controlled by a switch generallydesignated 8 whereby theforward or reverse windings of the motor l3 areconnected in circuit to govern the forward, or reverse rotation of thismotor. Across .a portion of the operating network there is connected theprimary winding ll of transformer l'l, being adjustably connected attapped points such as "a and a. onthe resistors II and 23, while thesecondary winding 04 of this transformer is connected in series with arectifier l3, for which will be hereinafter set ay' referring to Fig. 2it will be noted that the reversible motor II has a fly-wheel 2| mountedon its shaft to retard the starting motion of the motor in order toprevent it from reaching a rela- (CI. 7E1) tively high speed on verysmall temperature changes. The shaft 22 of the motor drives the worm 23which engages the worm gear 24. This worm gear, which rotates on theaxis 25, carries the slide wire resistor I to change the relation ofthis element with respect to the stationary wiper I, and also carries adrum 26 which drives a metal tape 21 carrying a stylus 28. The movementof this tape is guided by the rollers 29 and 30 to move the stylus 28transversely across the chart 3i, which is driven by a rotating roll 32carried by the shaft 33. This shaft is driven by the worm thuscontinuously driven, carries the rotating cams 40, ll, and 42. As bestshown in Fig. 3, the cam til operates the link 43 by a reciprocatingmotion. This link is provided-with a slot 44 to receive the shaft 36 andis also provided with a. roller or cam follower 45 to engage theperiphery of the cam 40. The link 43 at its left end, as hereinillustrated, is pivoted at 46 to an arm 41, the upper end of which issecured to one end of the sleeve 48 having a portion passing through abearing in the supporting plate 49. At the other end of this sleevethere is secured a cam plate 50 notched at its upper edge as indicatedat 5i to engage a pin 52. The pin 62 is carried by a stepped lever 53pivoted in a suitable support (not shown) at point 54. The left end ofthis lever is so shaped that its upper edge is formed relatively closetogether, to restrict the swinging of the galvanometer needle to a verysmall movement in order that it may respond quickly. Thus these stopsserve to keep the galvanometer needle very close to the center pointbetween the stops, even in cases wherein their absence the galvanometerneedle would have a large deflection. By this arrangement thegalvanometer needle can return to its center position in a minimumamount of time when the current through the galvanometer coil is reducedto zero. The right hand portion of the lever 53 has connected theretoathin flat spring which has fastened thereto the notched shutter plate 6I f It should be pointed out that the right hand end of the lever 33 isheavier than the left hand end so that when the pin I2 is not supportedby the cam 58, the right end of the lever will drop until some one ofthe portions 55,

88 or 51. at the left end thereof restsagainst the galvanometer needle88. As shown in Fig. 4, a plate 88 is supported on the upper ends of thestops 58 so that when the lever 58 is elevated to engage the end of thegalvanometer needle, this needle, although it is elevated slightly, isheld against abnormal upward movement by this plate.

It has been mentioned that the rotating shaft 88 carries cams H and 42.Cam 42-is engaged by the cam follower II mounted on the lever I2 whichlever is pivoted at its right hand end on the shaft 84. The free end ofthe lever I2 is formedwith steps as shown at 85a and 85b to engage theshutter plate 8|. Near the free end of this lever there is provided apin I8 which engages the slot 81 in the link 88. The upper end of thislink is pivoted at 88a to the switch actuating arm 88 which arm ispivoted at 18. The cam 4| is engaged by the cam follower 82 carried bythe lever 88 which is pivoted at its right hand end on shaft 84. Thefree end of the lever 88- is formed with steps the same in shape asthoseon the free end of the lever I2 and likewise cooperates with theshutter plate 8|. Near the free end of the lever 83 there is likewiseprovided a pin 88 which is received in a slot I4 in the lower end of thelink I5, the upper end of which link is pivoted at 1511 to the arm 89.The

free end of the arm 88 has a drum portion I8 a series of normally opencontactor springs Sid and 820, etc., to bring them into closedcondition.

By way of example, it isassumed that shaft 88 rotating at a speed of- R.P. M. will cause the left end of the lever 53 to be raised and loweredonce every second, through the action of the members including the lever43 and the cam plate 50 engaging the pin 52. This motion of the lever 58takes place in about one quarter of a second and its left end remains inits lowered position about three quarters of a second. During this lastinterval of time the galvanometer needle 581s free to swing and if thepotentiometer network 5 is balanced, the galvanometer needle 58 willremain in its intermediate position, that is, in the notch 51. If,however, the potentiometer network is unbalanced during this period ofunrestricted swing of the galvanometer needle 58, this needle will bedeflected to the left or to the right, as the case may be, until itrests against one of the stops 58. If it be assumed that thegalvanometer needle 58 has been deflected to the left, the lever 53 whennext released under the action of cam plate 58 will contact with thegalvanometer needle 58 at step 58. However, if the galvanometer needleis deflected to the right, the part 55 of the lever 58 will engage thegalvanometer needle. Thus these three possible positions of the lever 53provide three different ways of obstructing the motion of levers 88 andI2. The cams 4| and 42 are identical and hold the levers 83 and I2 inthe position shown in Fig. 3 for the greater part of each of theirrevolutions,

that is to say, for about seven-eights of a second.

During the remaining one-eighth of a second the notches in these camspermit the levers 83 and I2 to rotate upward around shaft 84 under thecontrol of springs such as 82. This motion of these levers, however, canonly take place when the two slots in the plate 48 are unrestricted bythe shutter plate 8|. It has been mentioned that and 4, both of theslots in plate 48 are partially obstructed so that the levers 88 and I2may rotate a small angle until steps 85b thereof rest against theshutter plate. In the second position of the'shutter plate, the upperslot (Fig. '4) in plate 48 is unobstructed while the lower slot thereofis completely obstructed so that lever I2 passes completely through theslot while the step 85a of lever rests against the shutter and keepsthis lever in its original position. In the third position of theshutter plate, the last-named conditions with respect to the shutterplate are reversed so that the lever 88 passes through the lower slotand lever I2 remains stationary. The notches in the cams 4| and 42 andin the cam 48 are so timed that the motion of the levers 88 and I2,requiring. about one-eighth of a second,

occurs within the quarter second period during -is pivoted at III torock the drum I8 with the projections 11 to 88 inclusive, to variouspositions, thereby closing various pairs of springs 'or contacts 9| and82 (Fig. 2) to complete different circuit combinations in the networksof Figs. 1 and 2. The drum and the pairs of springs actuated therebyconstitute a multiposition progressively movable switching means.

The operation of the systemis as follows: As long as the potentiometernetwork 8 is balanced, the galvanometer needle 58 remains in theposition shown in Fig. 4, that is, in engagement with the notch 51 oflever 58. with the lever 88 in this position, the levers 83 and I2 willactuate switch arm 89 with the result that either the projection I8 orI8 will be positioned to close contact between springs 82b and eithersprings Me or Sld, while springs 82a and 82c are open so that the motorremains at rest.

However, if the temperature to which the thermocouple 8 is exposedchanges, the potential across this thermocouple changes and unbalancesthe potentiometer network thereby causing current to flow through thegalvanometer coil and resistors II and I2 with the result that thegalvanometer needle 58 will be deflected from its intermediate position.If it be assumed that the galvanometer needle is deflected toward theleft, the switch drum I8 will be operated to close the two pairs ofswitch springs, 82c with Me and 92a with Sla, as indicated in Fig. 1.The closing of these springs will immediately cause the motor I3 tooperate in a circuit traceable from the alternating current source,conductor 85, spring 82a, spring 8la, motor field I4, armature I8,resistor I 8, conductor 88, to the other side of the A. C. source. Themotor I8 willrotate the slide wire resistor I with respect to thecontact 8 in the proper direction untilthe potentiometer network isagain balanced. On the establishing of this balanced condition, theneedle 58 will then return to its intermediate position and consequentlythe switch arm through the action of links 88, I5 and the levers 88 andI2, will be moved to a position where the switch drum I8 will berestored to one of its intermethe operating circuit of the motor lustdescribed is interrupted and at the some time the motor. isshort-circuited over a path traceable from the lower terminal oi. thearmature ll, conductor 81, spring 02b, spring Ole, iield windim II, andthe upper terminal oi the armature, which circuit causes the motortobecome a sbort-circiuted generator, thereby acting as a powerful brake.Therefore; when the switch is moved to open the operating circuit 0!the'motor, the motor will be'stopped very quickly. Ina similar manner,the reverse operation of the system is eiiected, that is, the motor IIwill operate in the opposite direction when the galvanometer needle IIis deflected toward the right. i

In order to prevent overthrow oi the stylus 28, an anticipatingarrangement is provided in the system oi'this invention. As hereindisclosed, this arrangement consists of an auxiliary circuit includingthe resistors II and 2| which are tapped at the points Ila and lla'iorconnection with the primary winding ll of a small transformer II. Thesecondary winding ll of this transformer is connected in series withrectifier SI and through springs 02c and springs Ole or 0|! with eitherresistor II or l2. It will be understood that the primary winding of thetransformer I1 is energized through the potential diiIerence between thetaps "a and 20a. The current thus induced in the secondary winding ofthis transformer after passing through the rectifier 98 and the springsMe in engagement with spring Qle or 9!! through either the resistor H orII, flows back to the secondary winding 94 of the trans former. If, forexample, spring 920 is in engagement with spring lie, current flowing inthe lastdescribed anticipatingcircuit including the resistor II, willdevelop a diflerence in potential across this resistor in the samedirection as the difference of potential set up across this resistor,due to current flowing therethrough in the previously mentioned circuitincluding thermocouple 9, the resistors l2 and II and the galvanometercoil. The difference in potential established by the anticipatingcircuit and the resulting current, increase thediflerence' in potentialacross the resistor II and thereby decrease the current through thethermocouple l and the galvanometer l0, so that the galvanometer needleswings to its zero position sooner than it would otherwise. Theconnections are so made that this anticipatory eflect will always tendto advance the galvanometer needle 58 toward its normal intermediateposition, so that the needle will reach this position a short timebefore the potentiometer slide wire I has reached the balance point.Through the switch mechanism previously described, the motor operatingcircuit will be opened before the balance point is reached, but themotor will continue to operate due to the inertia of the armature ituntil the braking action resulting from the short circuit, as well asfriction of all of the moving parts bring it to a stop. The anticipatoryarrangement should be so designed as to bring the motor from full speedto a complete stop either at the exact balance point of the slide wireor very slightly before this point is reached.

It will be appreciated that with small deflections of short duration ofthe galvanometer needle 58, the motor does, not reach full speed and themotor current is therefore higher than the full speed'current, However,as the motor speed increases, the motor current decreases and will causea corresponding change in the difference of potential between the tapsIla and 20a. Consequently, the potential-in the anticipatory circuitwill vary gradually and by selecting proper resistance values forresistors II and II and with suitable location of the taps "a and a, theanticipatory efl'ect' can be so designed as to operate eiIectively forlarge as well as for small galvanometer deflections. From the foregoingdisclosure it will be seen that the mechanical devices forming a part ofthis invention are of rugged construction, and include unusually fewbard application, Serial No. 657,232, flied Feb.

17, 1933, originally flled in the names 0! Hubbard and Widmer, nowPatent No. 2,025,749, granted December 31, 1935.

I claim:

1. In a device of the class described, an instrument provided with amovable index, an oscillatably mounted strip having a notched side edgeand a slotted end portion, means for periodically moving the notchededge of said strip into engagement with said index to position saidstrip in accordance with the setting oi. said index, said strip beingmovable at right angles to the plane of movement of said index,rotatively mounted elements periodically movable in timed relation tothe periodic movement of said strip, said elements being movable intoengagement with the slotted end portion of said strip in accordance withthe position oi. the slotted portion thereof, a pivoted member to bepositioned, and links respectively connected to said member at oppositesides of said pivot and to said elements for selectively positioningsaid member.

2. In a device 01' the class described, an instrument provided with amovable index, an oscillatably mounted strip having a notched edge and,a slotted end portion, means including a cam for periodically moving thenotched edge of said strip into engagement with said index to positionsaid strip in accordance with the setting of said index, said stripbeing movable across the plane of movement of said index, elementsselectively movable into engagement or out of engagement with said stripin accordance with the position of the slotted portion of said strip,cam means for moving said elements periodically in timed relation to theperiodic movement of said strip, a single rotating shaft on which saidcam and said cam means are mounted, a member to be positioned, and meanscontrolled by said elements for selectively positioning said member.

3. In a device of the class described, an instrument provided with a.movable index, a. strip having a notched side portion and a slotted endportion, means for periodically moving the notched portion of said stripinto engagement with said index, elements selectively movable topositions determined by their engagement with or by their lack ofengagement with said slotted portions in accordance with the position ofsaid strip, a movable member, and means including said elements forselectively positioning said member.

4. In a device of the class described, a galvanometer provided with aswing needle, an oscillatable strip having a notched portion. and aslotted portion, means for periodically moving the notched portion ofsaid strip into engagement with said needle to position said strip inaccordance with the setting or said needle, said strip being movable ina plane. intersecting the plane of movement of said needle, elementsselectively movable in a plane at right angles to the plane of movementof said strip, said elements being movable to positions determined bytheir engagement with or by their lack of engagement with said slottedportion in accordance with the position of said strip, a member, andmeans including said elements for selectively positioning said member.

5. In a device of the class described, an instrument provided with amovable index, a strip having a notched edge and a slotted portion,means for periodically moving the notched edge 01' said strip intoengagement with said index to position said strip in accordance with thesetting of said index, said strip being movable in a plane intersectingthe plane of movement of said index, oscillatably mounted elementsselectively movable in a plane intersecting the plane of movement. ofsaid strip, said elements being movable in accordance with the positionoi the slotted portion of said strip, a pivoted member to be positioned,and links respectively interconnecting the end portions of said memberand said elements for selectively positioning said member.

6. In a device of the class described, an instrument provided with amovable index, an oscillatably mounted strip having a. notched edge anda slotted portion, means for periodically moving the notched edge ofsaid strip into engagement with said index to position said strip inaccordance with the setting of said index, said strip being movable atright angles to the plane of movement of "said index, elementsperiodically movable in timed relation to the periodic movement of saidstrip, said elements being movable in accordance with the position ofthe slotted portion oi said strip, a pivoted member to be positioned,and links respectively connected to said member at opposite sides ofsaid pivot and to said elements for selectively positioning said member.

JULES A. WIDLER.

